The present invention relates to armature and needle assemblies for fuel injectors for internal combustion engines.
In known fuel injectors, a specific length of needle is required for each particular application. In order to provide a needle for a different application, it is often necessary to design and manufacture a different size needle. Such a requirement is costly and time consuming. It would be beneficial to provide a fuel injector having a needle with a variable length, which can be adjusted to meet the required needle length for the specific application.
Additionally, known fuel injectors presently use a relatively large armature to which the needle is connected. During operation of the fuel injector, a magnetic field generated in the fuel injector reciprocates the armature and the needle to open and close the fuel injector. Such a relatively large armature requires a correspondingly large magnetic force to move the armature. Additionally, the relatively large size of the armature results in a relatively large cost to manufacture the armature. It would be beneficial to provide a smaller, lower cost, armature.
Briefly, the present invention provides a fuel injector comprising a hollow body having an upstream segment and a downstream segment and a valve. The valve has a needle assembly reciprocably mounted in the hollow body. The needle assembly includes an upstream segment having a first longitudinal channel extending therethrough and a magnetic armature located within the first longitudinal channel. The armature includes a passage extending therethrough. The needle assembly also includes a downstream segment having a second longitudinal channel co-axial with and communicating with the first longitudinal channel. The second longitudinal channel extends through the downstream segment. The downstream segment also includes a seating body located at a downstream end and a transverse passage located upstream of the seating body. The transverse passage communicates with at least one of the first and the second longitudinal channels. The valve also includes a seat disposed downstream of the needle assembly. The seating body is adapted to sealingly mate with the seat when the needle assembly is in a closed position.
The present invention also provides a needle assembly for a fuel injector. The needle assembly comprises an upstream segment having a first longitudinal channel extending therethrough and a magnetic armature located within the first longitudinal channel. The armature includes a passage extending therethrough. The needle assembly also includes a downstream segment having a second longitudinal channel co-axial with and communicating with the first longitudinal channel. The second longitudinal channel extending through the downstream segment. The downstream segment also includes a seating body located at a downstream end and a transverse passage located upstream of the seating body. The transverse passage communicates with at least one of the first and the second longitudinal channels.
The present invention also provides a method of fabricating a needle for a fuel injector. The method comprises providing an upstream segment having a first longitudinal channel extending therethrough; providing a downstream segment having a second longitudinal channel extending therethrough, the downstream segment further having a seating surface and a transverse opening extending therethrough upstream from the seating surface; aligning the first longitudinal channel co-axially with the second longitudinal channel; inserting one of the upstream segment and the downstream segment into the other of the upstream segment and the downstream segment; and fixedly connecting the upstream segment and the downstream segment.